Some pteridologists recognize a narrowly defined Lycopodiaceae s.s. and Huperziaceae with the latter comprising Huperzia, Phlegmariurus, and Phylloglossum Kunze, considering that the split between Huperziaceae and Lycopodiaceae s.s. has been dated to ca. 350 million years ago using plastid rbcL data (Wikström & Kenrick, Molec. Phylogen. Evol. 19: 177-186. 2001), an age much older than many extant fern families/orders. In spite of this, here Lycopodiaceae s.l. including Huperziaceae is recognized because of the sister relationship between Huperziaceae and Lycopodiaceae s.s.

In the Lycopodiaceae, sometimes Lycopodiastrum is subsumed under Lycopodium. However, the split between Lycopodiastrum and Lycopodium s.s. has been dated to the Permian Period (251-299 million years ago), much earlier than when extant species of Lycopodium s.s. started to diversify (Wikström & Kenrick, loc. cit.). Also, the morphology of Lycopodiastrum is distinct from Lycopodium. Therefore, Lycopodiastrum is recognized here.